| 1. |
- Brynzér, Henrik, et al.
(författare)
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Design and performance of kitting and order picking systems
- 1995
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Ingår i: International Journal of Production Economics. - 0925-5273. ; 41:1-3, s. 115-125
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Tidskriftsartikel (refereegranskat)abstract
- The results from a number of case studies carried out within a research project concerned with the design and performance of materials kitting systems are discussed. The focus is on the design of the kitting systems in terms of location of the order picking activity, work organization, picking method, information system and equipment. These design considerations are related to performance measurements, such as picking efficiency and picking accuracy, and are discussed in relation to the preconditions of the kitting system. In kitting systems, results show that picking efficiency and accuracy can be improved by making better use of the product structure when designing the picking information and when deciding the storage assignment policy. Also, batching of picking orders is cost efficient when extensive sorting and administration can be avoided. In general, combining the work roles of assembly and picking results in less administration.
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| 2. |
- Gadde, Lars-Erik, 1945, et al.
(författare)
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Utvecklingslinjer i byggsektorns distributionssystem
- 1999
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Ingår i: In Bröchner, J. and Josephsson, P-E. (eds) Proceedings of the Nordic Seminar on Construction Economics and Organization, pp. 171-178. Chalmers University of Technology, Sweden. ; , s. 171-178, s. 171-178
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Konferensbidrag (refereegranskat)
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| 3. |
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| 4. |
- Blinge, Magnus, 1963
(författare)
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ELM: Environmental Assessment of Fuel Supply Systems for Vehicle Fleets
- 1998
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis is based on the idea of applying a logistics approach to fuel supply systems. The complete supply chain from energy raw material to end use in the vehicle is analysed while keeping track of energy conversion efficiency, exergy consumption and emissions to air. This method, which is referred to as Energy Logistic Modelling (ELM), is heavily influenced by LCA practices. The viability of using this approach in the decision-making process of choosing fuel for a vehicle fleet is investigated. The emphasis is on organising and structuring life cycle inventories of fuels for entire fleets of vehicles and to give recommendations and guidelines for how to define system boundaries and allocation rules. ELM is suitable for assessing trade offs between changes of fuel or system boundaries and the above mentioned fuel supply chain measures, as well as technical modifications of the supply chain itself.
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| 5. |
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| 6. |
- Franzén, Stig, 1943
(författare)
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Public Transportation in a Systems Perspective A Conceptual Model and an Analytical Framework for Design and Evaluation
- 1999
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Today urban areas are faced with problems like traffic congestion, air pollution, and limited accessibility and transport policy issues are focused on the "sustainable city of the future". For decision-makers the crucial question is how, with limited financial resources, a system for public transportation should be designed and developed to provide attractive travel and transport services. The basic problem is related to the systems design process itself, as the introduction of advanced applications based on new information and communication technologies will require a better understanding of public transportation in a systems perspective. By combining cognitive systems engineering and transportation systems analysis, relevant elements of control and communication theories (cybernetics) and human factors, a conceptual model and an analytical framework for public (mass passenger) transportation are developed. By use of a means-ends hierarchy of functional levels, the model describes five dynamic processes (the accessibility, travel, transport, traffic, and motion processes) in public transportation. Structural elements of the model (nodes for control functions, information collection and processing, and links for data and information flows) and their characteristics are identified and discussed. The framework and the model are, for validation purposes, applied in a design task (the realisation of an information centre for travellers and passengers) and in an evaluation task (an exploration and analysis of how incidents and disturbances are handled in Gothenburg). The complexity of public transportation is further explored, and control and data filtering needs on each functional level are identified and related to the potential of future dynamic interaction between actors on different functional levels. It is finally stated that the systems approach used to develop the model and the framework will become a necessary basis for future new ideas of how to promote the transportation of people by public means and, in that respect, the concept of intermodal passenger transport is critically assessed. The potential of the conceptual model and the analytical framework, to incorporate all possible means of transport (public and private) as well as to apply to the transportation of goods, is also discussed.
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| 7. |
- Hagman, Thore E.W. 1952
(författare)
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Logistic Time Requirements in Fast Sea Transportation Systems
- 1998
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The dissertation deals with logistic time requirements in fast sea transportation systems and the benefit of the application of the total time definition. The transportation engineering approach, to create new transport systems with high effectiveness, high service levels and also with high resource utilisation, has to some extent gained acceptance in the transportation industry, but it has not been fully realised that the transport system and the traffic system are not identical and that by focusing on high performance of the traffic system no guarantee is given that the transport system will become effective. This may be the explanation why, in the present rush for introducing high speed passenger services, the support systems have not been designed to match the performance at sea and the high energy and capital costs associated herewith. The main objective for moving passengers is normally to obtain the shortest possible time in the transport system. This goes for all transportation modes; air, land and sea and it has for waterborne transportation led to a shifting of interest from conventional ferries to fast ferries. In recent years speed at sea has been doubled at some ferry services, and as a consequence, sailing time has been reduced accordingly. Logistic time requirements in a ferry operation are related to the performance of the main system, the movement system and the supporting subsystems, like access systems, and if these work in sequence or to some extent in parallel. Time requirements in ferry operation can be divided into two categories; one operational category which includes cycle, sailing, and terminal time, and one category referring to the user of the provided service perspective, the total time. The total time is the time definition which is the most relevant to the passenger, as this is the time the passenger has to spend in the actual transportation system. An example (paper No IV) shows that an increase of the speed with 100% in the vessel movement system only gives a reduction of the total time in the transport system with 15%. The thesis includes six papers reporting data collected from fast and conventional sea transport systems.
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| 8. |
- Hultén, Lars A. R., 1964
(författare)
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Container Logistics and its Management
- 1997
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In this work research on container logistics and its management is presented. Contrary to the common approach of treating this as a mathematical problem and addressing it by operations research methods, this work regards the problem in a wider perspective. Instead of being limited to management of the physical system bringing about the movement of containers, container logistics management is regarded as also including demand management. The research aims at describing the logistics of the system in terms of how the various components in a container transport system interact and how the system interacts with its environment. Due to the limited previous research on container logistics and its management in a wider perspective, this work is primarily explorative and descriptive. Empirical studies of container flows are presented. Both the flow for an individual carrier and the total flow between a port and its hinterland have been studied and the studies reveal a low utilization of the containers. Containers were found to be stored empty for long periods of time at terminals, retained for a considerable time by customers and there was much transport of empty containers. The studies also revealed poor quality of the data in the computerized tracking systems with missing and erroneous data entries. In a study of ten of the world's twenty largest container shipping companies it was found that the use of advanced decision support systems, taking advantage of operations research or artificial intelligence technology, was scarce. Only one company reported to use such a system, which assigned priorities to depots, in day-to-day operations. The main logistical functions of the container are to create opportunities to exploit economies of scale and enabling vessels and vehicles to operate independently by decoupling them at terminals. Therefore, when deciding on actions to improve the utilization of containers the effect on other system components must be considered. Pooling is suggested as a way of increasing the utilization of the containers without constraining the operation of other, capital intensive, resources. Container logistics systems are characterized by high complexity and uncertainty. Much of the information relevant for decision-making is informal and the managers' experience is difficult to formalize. Therefore successful systems for container logistics management must take advantage of both human and computerized information processing. It is suggested to engage theories from cybernetics and information theory as a theoretical framework for logistics systems analysis. Even if this is only done to a limited extent in this research, due to being considered at a late stage of the research, these theories show a strong explanatory ability.
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| 9. |
- Jahre, Marianne, 1963
(författare)
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Logistics Systems for Recycling - Efficient Collection of Household Waste
- 1995
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This dissertation investigates collection and recycling of household waste with focus on packaging materials. The purpose is how to describe and explain the d esign of a collection system according to different system environments in orde r to achieve high logistics performance in terms of low cost and high service. The research approach consists of two main parts. First, data on existing syst ems are collected and analysed. Then a model is used to analyse cost consequenc es from changes in the system and the environment. Four main properties of reverse distribution channels were identified including the number of distribution levels and distribution points, whether the system is bring or kerbside, the degree of separation at source and the degree of co- collection. The study further demonstrates that performance can be measured in a number of ways including service toward end-markets and households, costs, en vironmental consequences and programme ratios. Finally, two main environmental factors identified were population density and the number of materials being co llected in the system. The major conclusion from the study is that systems in areas with low populatio n density should collect and recycle few materials that should be separated at the source and then co-collected. Systems in areas with high population density, on the o ther hand, may collect many materials, but then centralized separation (i.e. processing in a MRF) should take place.
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| 10. |
- Lindau, Roger, 1961
(författare)
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The Impact of High-Quality Information on Performance in Manufacturing
- 1995
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The dissertation deals with the impact of high-quality information on performance in manufacturing. In a system where two material flows with sequence dependency are matched, the use of real-time information to monitor and control the sequencing buffer improves the system's ability to schedule many different models, compared with a system with no information at all. In the latter case, the system is upset considerably when more than four different models enter the system. The use of automatic data capture systems enhances productivity in manufacturing companies. Six case studies were carried out, all of which showed that the productivity improvements obtained by these systems are mainly in the area of human resource utilisation which was found in all six case studies. Improvements in machine utilisation, transporter utilisation and inventory levels were also found. The productivity can furthermore be improved if the installed system acts as a proactive system, giving information on the operational level about deviations and changed customer demands. Out of 31 registered disturbances, 15 resulted in a productivity loss because scheduling information was not available. A system providing scheduling information makes it possible for the scheduler to change a dispatch list or final assembly schedule in such a way that a less important job can be run ahead of a delayed important job, only to release capacity when the delayed job arrives. These kinds of systems mainly enhance productivity in an environment with shared resources. The impact of providing the scheduler with real-time information of high quality is investigated. It is shown that this enables him to reschedule the work force when stochastic events such as disturbances of different kinds affect the scheduling environment. It is also shown that the performance of the scheduled system improves a/ in direct relation to the number of work stations being scheduled and b/ with the reduction in lapse between the detection of a deviation and corrective action. Measures taken to prevent the propagation of disturbances can be classified as formal measures and informal actions. Formal measures are such measures which are defined in a computer system, and informal actions are such that are executed manually. None of the measures identified in this study were efficient when a holistic evaluation was made. This evaluation describes the ability of the measure to absorb disturbance effects, its cost and the degree to which it upsets the system. Some measures were, however, better than others. Partial delivery is a suitable action when materials shortages occur, subcontracting when machines break down, and moving over personnel when absenteeism occurs. When an ADCS is used, two types of effect can be experienced; direct effects and indirect effects. The direct effects are the result of the data capture process as such being enhanced, i.e. less effort is needed to capture data and to trace and correct faulty data, and the indirect effects are the effects experienced when timely and accurate data is fed into the data base from which a number of functions retrieve the data. The direct effects are normally easy to define. They affect the number of staff involved in data capture and handling, and in some cases safety stock levels. Indirect effects are more difficult to isolate. A general model showing the manufacturing process and the different ADCSs which can be found within each activity was developed. Indirect effects experienced as a result of enhanced decision-making when an ADCS is installed were; increased sales, decreased costs and decreased inventory investments. Both direct and indirect effects enhance the effectiveness of a company. It is shown how the use of a serial information flow respectively a parallel information flow with different time delays affects the performance of a system when expediting is carried out. The results indicate that a parallel information flow, i.e. information to the succeeding activities being given in advance, performs best if the information quality is high, i.e. the time delay is close to zero. When the time delay increases there is a threshold when the serial information flow performs better than the parallel information flow with poor information quality. The performance of the parallel system decreases with poor information quality. The same result is obtained with respect to the output, i.e. the output decreases with poor information quality.
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